Age-dependence of the rat Leydig cell and Sertoli cell function. Development of the peripheral testosterone level and its relation to mitochondrial and microsomal cytochromes P-450 and to androgen-binding protein.

The first part of this study compares peripheral testosterone levels with intratesticular levels of the cytochromes P-450 of two key enzymes of androgen biosynthesis, i.e. mitochondrial cholesterol monooxygenase (P-450(cscc)) and microsomal steroid-17 alpha-monooxygenase (P-450(C17 alpha)) during puberty and early adulthood of male Wistar rats. From 4 to 10 weeks of age, the testosterone level increases 8.7-fold, the P-450(C17 alpha) level 8.3-fold, but the P-450(cscc) level 24.5-fold as an indication of specific induction of this protein. From 13 to 50 weeks of age, the testosterone level remains constant, the P-450(cscc) level increases continuously by a factor of 1.4, but 62% of the P-450(C17 alpha) content are lost. This discrepancy is explained by a divergent regulation of the cytochromes P-450 of the two steroid monooxygenases: a persisting induction of P-450(cscc) and a concurrent down-regulation of P-450(C17 alpha) that may be a consequence of the high rate of Leydig cell steroid hydroxylation after puberty. Overlapping of both processes may (probably besides other developmental factors) result in a constant testosterone concentration in blood. The second part of the study compares testicular and epididymal levels of androgen-binding protein (ABP) with the peripheral testosterone level. The peripubertal increase in testicular ABP content is shown to be related only to the increase in testicular mass, whereas a specific accumulation of ABP occurs in the epididymis from 4 to 13 weeks of age. This pattern indicates an increasing secretory activity of the Sertoli cells that remains high during adulthood up to the 50th week.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of streptozotocin-induced hyperglycaemia on androgen-binding protein in rat testis and epididymis.

In adult male rats treated with streptozotocin 6 weeks before the experiments, androgen-binding protein concentration was increased in testicular tissue by 33% (p less than 0.01) and reduced in epididymal tissue by 25% (p less than 0.005) in animals exhibiting severe hyperglycaemia as compared with animals remaining in normoglycaemia or moderate hyperglycaemia. Androgen-binding protein content was diminished in epididymal tissue by 40% (p less than 0.0005) but not changed in testicular tissue. If related to constant body weight, the sum of testicular and epididymal androgen-binding protein was identical in both normo- and hyperglycaemic animals. This disturbance in androgen-binding protein distribution may be the consequence of altered testicular secretion or impaired transport of androgen-binding protein from testes to epididymides.